In the prior art, a fan rotor disk comprises a plurality of vanes mounted around its perimeter and separated from each other by platforms fixed to disk flanges. Each vane is made up of a blade connected to a vane root by an intermediate section. The vane roots are engaged in grooves formed essentially axially in the perimeter of the disk and are held in these radially by the interlocking of their shapes, the vane roots being for example dovetailed or the like in transverse section.
When the turbomachine is operating, loss of the connection of a vane to the disk can result in the destruction of the neighboring vanes and associated platforms. What happens is that if a fan vane is lost, it pushes against the neighboring vane, and the resulting force applied to this vane causes in particular an axial stress directed in the upstream direction because of the angular setting of the blade relative to the groove, which tends to make the vane twist upstream and generate a large stress in the rear connection between the vane root and the disk. The vane root or a tooth of the disk may then break, causing a chain reaction which can destroy all the vanes of the fan as well as the platforms and seriously damage the turbomachine.
In certain types of vane, the vane root, which is engaged in the groove, is connected downstream to a hook. Recesses formed radially on either side of each hook engage with an annular plate so as to keep the vanes in the axial position when positioned in the grooves of the disk. In the event of loss of a vane, this fixing method generates a large stress in the connecting region between the intermediate section and the hook and in the connection between the recess and the hook. As before, this stress can result in a breakage, at the vane hook or in the disk, and can cause a chain destruction of the vanes and platforms.
In the prior art, an axial groove of approximately 10 mm length, leading to the recess, is machined on each side of the vane root, to limit the stress applied to the intermediate section/hook connecting region and to the recess/hook connecting region, by directing the forces upstream of the machined notch. Although this groove limits the forces at the hook, its disadvantage is that it generates a stress peak at its upstream end, resulting in serious wear of the vane root and of the disk and thus limiting their life. A number of solutions have been envisioned to limit the wear of these parts and have involved removing material at the upstream end of the machined notch, or fitting a shim between the vane and the disk. However, these means do not satisfactorily resolve the problem of wear by limiting the stress applied to the vane hook and transmitted to the platforms.
It is a particular object of the invention to provide a simple, inexpensive and effective solution to these various problems.